The present invention relates to sickle-type mowers and more particularly relates to cutter bars including a pair of sickle or knife assemblies.
As mowing machines such as windrowers or mower conditioners and the like have become larger, it has become necessary to use cutter bars including a pair of sickle assemblies in order to reduce the mass of a given sickle assembly and in that way reduce forces. While the usage of two sickle assemblies per cutter bar has reduced forces, it has given rise to the problem of how to design the sickle assemblies so that crop encountered by the central portion of the cutter bar, where the two sickle assemblies meet, is cut.
U.S. Pat. No. 3,577,716, granted on May 4, 1971, discloses a twin sickle cutter bar designed or ensuring that crop encountered by the middle portion of the cutter bar is cut. However, the design requires that an end knife of one sickle assembly be arranged to cut against an end knife of the other sickle assembly. This then requires that the drives for the two sickle assemblies be timed so that the end knives meet for proper cutting. Also the design requires that the end knife of one of the sickle assemblies be inverted, thus requiring special attention during manufacture of the sickle assembly.
U.S. Pat. No. 4,246,742, granted on Jan. 27, 1981, also discloses a twin sickle cutter bar design wherein end knives of one sickle assembly cut against end knives of the other sickle assembly, and therefore, also requires the drives for the sickle assemblies to be timed for proper cutting operation. Also, certain ones of the knives are special since they are unsharpened.
U.S. Pat. No. 4,236,370, granted on Dec. 2, 1980, discloses a twin sickle cutter bar design wherein the end of one sickle is provided with an extension that carries inverted knives which cut against upper ledger surfaces of a set of special knife guards having upper and lower ledger surfaces.